1. Field of the Invention
This invention relates in general to an implantable artificial kidney, more particularly a miniature life-sustaining blood purifying hemocatharsais unit, maintaining acceptable homeostasis when implanted in patients with chronic end stage renal disease, sutured to a major artery, vein and ureter, functions with no extra-corporeal connections nor interactions. Obtainable without a living or cadaver donor, eliminating the required 0 to 6 antigen matching and the immunosuppressive, anti-rejection medication required for the lifespan of all donated human kidneys.
2. Background of the Invention
The Human Urinary System is made up of the kidneys, the bladder, two ureters, and a single urethra. The kidneys are a pair of organs resembling large kidney beans. In the average adult, measuring around 4″ to 5″ long and 2″ to 3″ wide, and situated against the rear wall of the abdomen, in the middle of the back, located on either side of the spine, beneath the liver on the right, and the spleen on the left.
Healthy kidneys in the average adult process about 125 ml/min or 180 liters of blood each day to filter out about 2 liters of waste product and extra water in the urine. The kidneys remove excess minerals and wastes and regulate the composition of the blood by keeping the concentrations of such inorganic ions as sodium, phosphorus, and chloride in the blood plasma at a nearly constant level. Potassium is controlled by the kidneys, for proper functioning of the nerves and muscles, particularly those of the heart.
Blood urea nitrogen (BUN), a waste product produced in the liver as the end product of protein metabolism, is removed from the blood by the kidneys in the Bowman's capsule, along with Creatinine a Waste Product of creatinine phosphate, an energy storing molecule, produced largely from muscle breakdown. High values, especially with high BUN levels indicate problems with the kidneys. When the kidneys are functioning properly and the concentration of an ion in the blood exceeds its kidney threshold value, the excess in the filtrate is not reabsorbed but is released in the urine thus maintaining near constant levels, the same is so with excess protein. This is done by the mechanisms of reverse osmosis, osmosis and ion exchange filtration.
Most kidney diseases attack the nephrons, causing them to loose their filtering capacity. The two most common causes of kidney disease are diabetes and high blood pressure. Diabetes keeps the body from using glucose as it should. If glucose stays in the blood instead of breaking down, it can act like poison and damage the nephrons. High blood pressure can damage the small blood vessels in the nephrons. The damaged vessels cannot filter poisons from the blood as they should. If the problems worsen and renal function drops below 10 to 15 percent, that person has end stage renal disease. When a persons kidneys fail, harmful wastes build up in their body, their blood pressure elevates and the body retains fluid.
That person will soon die unless their life is temporarily prolonged by either a kidney transplant or dialysis. If the patient chooses a kidney transplant their immune system attacks the foreign kidney, requiring that the patient take immunosuppressants the rest of their life. If the patient chooses dialysis their electrolytes, especially phosphorus will become unmanageable; this plays a big role in the cardiovascular mortality rate being 20 to 40 times higher for adults on dialysis than for the general population.
Dialysis machines are the most widely used temporary lifesaving invention for patients with end-stage renal disease. Hemodialysis machines are described as large stationary hydro-mechanical devices. In order to make them functional they require many accessories such as an arterial line, blood pump, heparin infusion pump, dialyzer filter, venous line, monitors to measure blood flow and pressure, air/foam detectors, motors, regulators and piping to carry 500 to 800 mL/min of dialysis solution with water and measured amounts of calcium, magnesium, sodium, potassium and other minerals, from large mixing-holding vats to the patients dialyzer, and from there to the drain. With hemodialysis the patient must be dialyzed three times a week; each treatment lasting from three to four hours. Although the dialyzers are removing poisons, there are side effects caused primarily by the dialyzers themselves.
The dialyzer filters are made of cellulose acetate, polysulfone or similar materials and sterilized with a solution of ethylene oxide, bleach or formaldehyde, none of which is suitably biocompatible. Dialyzer filters have just one membrane pore size with a cut-off point just larger than creatinine at 113.12 atomic mass units (AMU). Removed with the creatinine is urea at 60.06 AMU, water and essential electrolytes such as sodium, potassium, calcium and magnesium are removed by the dialyzer but not replaced during dialysis.
Phosphorus molecules at 123.92 AMU, are not removed by dialysis and large amounts are deadly to the patient. Neither failed kidneys nor dialysis can remove phosphorus, requiring that large doses of calcium based phosphate binders be taken, leading to coronary calcification and eventual death for many dialysis patients. Other problems with dialysis is that the tubing blood pump crushes many of the patient's blood cells, inducing clotting, the machine is also known for overheating the patients blood.
3. Brief Summery of the Invention
This invention relates in general to a fully functional human kidney replacement unit, made of anticoagulant materials. Comparable in size to actual human kidneys. This device will provide patients who have end stage renal failure with an alternative to donor kidneys (graft), without having to combat rejection by taking immunosuppressive agents, often accompanied by side effects and infection. This kidney replacement unit whether worn outside the body extracorporeal, or implanted in the body by surgery, will provide patients with essential kidney functions, similar to those of real kidneys.
Unlike large cumbersome dialysis machines requiring long arterial lines, blood pumps and heparin infusion pumps, a dialyzer cartridge, venous line, blood flow monitors, pressure and air/foam detectors, and to further worsen the situation, the patient is troubled with hypertension, hypo-tension, headaches, nausea, blood loss, blood overheating, Blood imbalance, shortness of breath, respiratory arrest, itching, hives, edema, elevated pulse rates and arrhythmia, and unlike this invention with multiple membranes, dialysis machines have only one membrane pore size which is In the range of 117 AMU, sized to remove createnine at 113 AMU. Unfortunately at the demise of the patient, these large pores remove the smaller essential electrolytes and minerals such as sodium, potassium, bicarbonate, calcium and magnesium. Dialysis also removes vitamin B12, folic acid and pyrodoxin, essential in maintaining good health.
In the preferred embodiment, the implantable human kidney replacement unit, referred to hereafter in this disclosure as “the unit” though compact and smaller than human kidneys, contains a plurality of independent self cleaning membranes fixed in cartridges designed to sort and reject or re-inject certain molecules as regulated by the patients needs. Selecting molecules by their weight in atomic mass units, waste products such as creatinine and urea, are removed while homeostasis in the blood is maintained by keeping the volume of water in the body constant. This invention regulates the concentration of electrolytes in the blood, such as the positive sodium, calcium, potassium and magnesium cations, and the negative chloride, bicarbonate, phosphorus and sulfate anions.
When the concentration of an ion in the blood exceeds the threshold value, the excess in the filtrate is not reabsorbed but is released in the urine, thus maintaining near constant levels in the blood. The unit housing is constructed of smooth crack and leak resistant blood compatible materials. Preferably polyvinyl-chloride (PVC) co-polymer, having anti-coagulant and bacteriostatic properties. All the interior blood passages are without sharp corners and edges that would cause turbulence and damage the blood cells, thus inducing clotting.
The units case contains all the porting and slots for blood and filtrate pressure regulation and distribution to and from a plurality of individual membrane filters made of inert anti-coagulant materials, preferably platinum, affixed one on each side of individual frames, forming membrane cartridges. There is at least one cartridge sealed to each side of each glomerular chamber, referred to mostly hereafter in this disclosure as “chambers”. There is an overflow port and a pressure relief valve in the upper end of each cartridge. To maintain positive pressure, slightly less than arterial pressure in the chambers.
Blood leaving the first chamber is cleaner than when it entered. Pressure rises in the cartridge cavity between the two membranes because the larger molecules that penetrated the first membrane are too large to pass through the outer membrane, the pressure relief valve opens and urine spills over into the waste port down through the chamber dividers, next to but not intersecting the vertical slit. The vertical narrow slit in the divider between chambers reverse osmosis chamber (RO) three and osmosis-diffusion (OD) chamber four is not as wide as those in the first three RO chamber dividers.
This is to reduce the pressure in the OD chambers, while raising the pressure in the filtrate-collection annular space; therefore, the process occurring now in OD chambers four and five is osmosis and diffusion, where molecules are being selectively reabsorbed into the blood as needed.
The process taking place in chambers four (OD-4) and five (OD-5) Is “dynamic diffusion” which occurs when some of the water and substances such as sodium and calcium flow from a region where they are highly concentrated to a region of lesser concentrated until a state of equilibrium is reached. Diffusion occurs when a system is not at equilibrium, as is the blood substances in chambers four and five and the filtrate substance from the RO chambers, separated by semi-permeable membranes in cartridges four and five. Osmosis is the diffusion of liquid molecules across a semi-permeable membrane. All molecules not diffused and re-absorbed in chambers four and five will be forced out the valves in the top of the membrane cartridges and drain down through the vertical cavity, to the waste chamber and then to the ureter and bladder.
Ficks first law of diffusion states that a substance diffuses in the direction that eliminates its concentration gradient at a rate proportional to the magnitude of its gradient. It is the square of the distance that has an influence on the formula and it is proportional to the available area. The IAK membranes have short distances and large areas to speed the diffusion process.
The upstream side (left side) is beveled all around to funnel blood to the slot. The first three glomular process chambers from left to right are reverse osmosis (RO) chambers and are labeled RO1, RO2 and RO3, also shown numerically as 20,21 and 23. The other two chamber to the right are osmosis diffusion chambers and are labeled OD1 and OD2, shown numerically as 23 and 24. There are five membrane cartridges in the assembly, six reverse osmosis cartridges, three on side A labeled RO1-A, RO2-A, and RO3-A, and three on side B, labeled RO1-B, RO2-B and RO3-B. Four osmosis-diffusion cartridges. Two on side A labeled OD1-A and OD2-A, and on side B they are OD1-B and OD2-B
Looking down at the main housing is vertical cavities running through the chamber dividers. This is where waste, excess water or other chemicals are allowed to drain down to a waste chamber beneath the glomular chambers on the bottom of the main housing. On both sides, (A) and (B) of the glomular chambers in the main housing are recesses with the same geometry as the chambers but slightly larger in height and width, forming an all around ledge. These ledges are where the membrane cartridges will be housed and sealed. Further out near the outer edge on both side (A) and (B) is one large recess extending the full width and height of the main housing, except for a thin lip all around the parameter. This is where the main covers nest and seal.